The September 15, 2026 federal estimated tax deadline has passed. If you were required to make a quarterly payment and missed it — or paid less than expected — the most important step is not to ignore it.
Estimated taxes are part of the federal pay-as-you-go system. They commonly apply to business owners, independent contractors, partners, S corporation shareholders, investors, landlords, and others whose income is not fully covered by withholding. A missed payment does not automatically mean a major tax problem — but waiting can increase the potential underpayment penalty, and it may also leave you with a larger balance due later.
For taxpayers and business owners in Los Angeles, this is a good time to review the year so far and make sure the remaining 2026 tax plan still makes sense.
Who Generally Needs to Pay Estimated Taxes?
For individuals, including sole proprietors, partners, and S corporation shareholders, estimated payments are generally required when you expect to owe $1,000 or more in federal tax after subtracting withholding and credits. Corporations generally make estimated tax payments when they expect to owe $500 or more.
The IRS generally looks at whether you have paid enough tax during the year through withholding and estimated payments. In many cases, taxpayers can avoid an underpayment penalty if they paid at least 90% of the tax ultimately due for the current year, or 100% of the tax shown on the prior-year return — subject to special rules, including different thresholds for certain higher-income taxpayers. Because every tax situation is different, these percentages should not be treated as a substitute for an actual projection.
What Happens If You Missed the September 15 Payment?
The IRS may assess an underpayment of estimated tax penalty when required payments are made late or are too small. The penalty depends in part on the amount that was underpaid, how long the amount remained unpaid, and the applicable IRS underpayment interest rate.
If a payment was required and was missed, making the appropriate payment sooner can generally reduce the period for which an underpayment exists. Estimated tax penalties are not the same as ordinary late-filing penalties — the calculation is based on whether enough tax was paid throughout the year and when those payments were made.
Step 1: Confirm Whether You Actually Have an Underpayment
Before making a random catch-up payment, review your current-year numbers. Your income may have changed significantly since your original estimate — business income may be higher or lower than expected, investment gains may have increased taxable income, a property sale may have created a large capital gain, payroll withholding may have changed, or deductions and credits may be different than anticipated. If your income changed, your estimated payment requirement may have changed too. A current tax projection can help determine whether you are actually behind — and by how much.
Step 2: Recalculate the Rest of 2026
The next federal estimated tax payment for individuals is generally due January 15, 2027 for income earned during the September through December payment period. Rather than simply repeating the amount from an earlier quarter, this is an opportunity to recalculate based on the year-to-date picture — current business profit, W-2 and other withholding, interest and dividend income, capital gains and losses, rental income, self-employment income, major deductions, available tax credits, and prior estimated payments already made. For business owners, this is also the right time to review bookkeeping accuracy — a tax projection built on incomplete books can produce an unreliable payment recommendation. See Quarterly Estimated Taxes 2026.
Step 3: Consider Whether Income Was Uneven During the Year
Not every taxpayer earns income evenly throughout the year. If a large portion of your income arrived later in 2026, the standard quarterly calculation may not accurately reflect when the tax should have been paid. The IRS allows an annualized income installment method in certain situations, which may help taxpayers whose income fluctuates significantly during the year determine whether the underpayment penalty can be reduced. This can be particularly relevant for business owners with seasonal revenue, commission-based professionals, investors with large gains in a particular quarter, and taxpayers who sold a business or property during the year. The calculation is more complex, so it should be reviewed carefully before filing.
Step 4: Review Withholding as an Alternative
Taxpayers who receive wages may also be able to increase federal withholding through payroll rather than relying only on estimated payments — useful when there are only a few months left in the year. A revised Form W-4 can increase withholding from future paychecks. Depending on the taxpayer's circumstances, withholding can sometimes provide more flexibility than trying to correct every shortfall through separate quarterly payments.
Step 5: Use the Remaining Months for Year-End Tax Planning
A missed September payment can be a warning sign that your tax plan has not kept pace with your actual income. Instead of treating the issue as a single missed deadline, use it as a reason to conduct a broader year-end review. For business owners, that review may include confirming revenue and expenses are fully recorded, reconciling bank and credit card accounts, reviewing accounts receivable and payable, checking fixed assets and depreciation, reviewing owner contributions and distributions, evaluating retirement plan contributions, reviewing entity-level tax obligations, identifying potential year-end deductions, and estimating the remaining federal and state tax liability. The earlier this work is completed, the more options may still be available before December 31. See 2026 Year-End Tax Planning Timeline for California Business Owners.
Why This Matters More Than Simply "Catching Up"
The goal is not just to make another payment. The goal is to understand why the estimate was missed or inaccurate and prevent the same issue from carrying into year-end. If income is growing faster than expected, the remaining tax liability may also be growing. If bookkeeping is incomplete, the estimate itself may be unreliable. If withholding is too low, the problem may continue every pay period. A current projection gives you a clearer answer.
Key Dates
| Date | What's Due |
|---|---|
| September 15, 2026 | Third federal estimated tax installment for individuals |
| January 15, 2027 | Next estimated tax payment deadline for most calendar-year individuals |
Los Angeles business owners and individuals working through a missed installment often benefit from coordinating the catch-up review with broader year-end planning. See Tax Planning in Los Angeles.
Compliance Resources and Tools
- IRS — Estimated Taxes (accessed September 16, 2026).
- IRS — Publication 505 (2026), Tax Withholding and Estimated Tax (accessed September 16, 2026).
- IRS — Underpayment of Estimated Tax by Individuals Penalty (accessed September 16, 2026).
- IRS — Third Quarter Tax Calendar (accessed September 16, 2026).
- A missed September 15 payment does not automatically mean a major tax problem, but waiting increases penalty exposure.
- The underpayment penalty depends on the amount underpaid, how long it stayed unpaid, and the IRS underpayment interest rate.
- Confirm the actual underpayment with a current projection before making a catch-up payment.
- The next estimated payment is generally due January 15, 2027 — recalculate rather than repeating an old figure.
- The annualized income installment method may reduce the penalty for taxpayers with uneven income.
- Increasing W-4 withholding can sometimes provide more flexibility than additional estimated payments.
- A missed payment is a good trigger for a broader year-end tax and bookkeeping review.
References
- Internal Revenue Service. Estimated Taxes. irs.gov (accessed September 16, 2026).
- Internal Revenue Service. Publication 505 (2026), Tax Withholding and Estimated Tax. irs.gov/publications/p505 (accessed September 16, 2026).
- Internal Revenue Service. Underpayment of Estimated Tax by Individuals Penalty. irs.gov (accessed September 16, 2026).
- Internal Revenue Service. Third Quarter Tax Calendar. irs.gov (accessed September 16, 2026).
The information contained in this publication is provided for educational and general informational purposes only. It does not constitute tax advice, accounting advice, legal advice, or any other form of professional advice and does not create a client-professional relationship.
The content reflects tax law and regulations applicable on the date of publication only and is subject to change without notice. Examples and illustrations are hypothetical and do not represent any specific taxpayer situation. Past results or referenced positions do not guarantee future outcomes.
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